1. Field of the Invention
The present invention relates to an arrangement of a designation of a drive element number using mother boards interposed between an adapter, as an upper grade device, and a plurality of drive elements. A mother board is a printed circuit board having connecting portions enabling a connection between a plurality of circuits. The arrangement according to the present invention is used, for example, for an interface circuit used in connection with an adapter for a magnetic disk storage and a plurality of drive elements for the magnetic disk storage.
2. Description of the Related Arts
For example, in a magnetic disk storage apparatus in which a plurality of drive elements are controlled by a single adapter, usually one or a plurality of mother boards are connected between the tag bus line of the adapter and the plurality of drive elements. The designation of the drive element number is carried out by designation the potentials of a predetermined number of pins of the connecting portion of a mother board to a LOW or logic HIGH level of potential, in the mother board.
By connecting the drive portions to the mother board through connection arrangement, the acknowledgement of an own drive element number is automatically carried out by a drive element based on the condition of the connection predetermined connection pins, and a control of only a specific drive element having a drive element number coinciding with the drive element number designated from the adapter is carried out.
It is possible to use a plurality of mother boards which are interposed between the adapter and the drive elements, but the size of a print circuit board for a single mother board tends to be increased as the number of drive elements connected to the single mother board is increased; this increase of the size of a print circuit board for the mother board can be avoided if the plurality of mother boards are used.
When two mother boards, i.e., first and second mother boards, are used between an adapter and a plurality of drive elements, e.g., No. 0 to No. 7 drive elements, the first mother board is used for No. 0 to No. 3 drive elements, and the second mother board is used for No. 4 to No. 7 drive elements.
In each of first and second mother boards, connection terminals corresponding to, for example, bits b.sub.0, b.sub.1, and b.sub.2 of a drive element number, are included in connection terminals of a connecting portion for the drive side, to constitute the connections corresponding to the drive element numbers.
Nevertheless, a problem arises in that, since the drive element numbers of the drive elements connected to the first mother board are different from those of the second mother board, different arrangements of the connecting portions are required for the first and second mother board, and accordingly, the provision of two kinds of mother boards becomes necessary. This causes an undesirable complication of the structures of the mother boards, the occurrence of inadvertent failures in the drive element number designation, an increase of the number of components, complications of the manufacturing process, and an increase of the manufacturing cost.